The metrics, or engineering specifications, that you created in the preceding list should be directly related to the customer needs. In other words, if you have created an engineering specification, it should have some relationship to a need imposed by the customer or the marketplace. Use the table below to map your customer needs against the metrics (or engineering specifications). In many design and product development circles, the rows along the left is often referred to as the voice of the customer, while the columns across the top are often referred to as the voice of the engineer.